Treatment and after-treatment of metal with amine oxide-containing polyphenol compounds

ABSTRACT

A metal treatment solution comprising an effective amount of a soluble or dispersible compound which is a derivative of a polyphenol. The present invention comprises novel derivatives of polyphenol compounds useful in the treatment of the surface of metal articles. The present invention also encompasses novel surface treatment solutions or dispersions, and methods of using these solutions or dispersions. The compositions of the present invention include amine oxide containing polyphenol compounds and derivative thereof. The molecular weight of the polyphenols used in derivatives of the present invention have molecular weights of from about 360 to about 30,000 or greater. The resulting derivatives of the present invention typically have a molecular weight of up to about 2,000,000 with molecular weights within the range of about 700 to about 70,000 being preferred.

BACKGROUND AND SUMMARY OF INVENTION

The present invention relates to the field of protective and/ordecorative surface treatment of articles, particularly metals, plastics,and the like.

The present invention comprises novel derivatives of polyphenolcompounds useful in the treatment of the surface of metal articles. Thepresent invention also encompasses novel surface treatment solutions ordispersions, and methods of using these solutions or dispersions.

In accordance with the present invention, novel compositions, solutionsand dispersions, and methods are provided for use in providing aprotective or decorative metal surface treatment; these include thetreatment of previously untreated bare metal surfaces, thepost-treatment of phosphatized or conversion coated metal surfaces, theapplication of a paint or other decorative coating or film, and thelike. The present invention additionally includes compositions andmethods that are particularly useful for treating various metal surfacesincluding aluminum, steel and zinc metal surfaces. The compositions,solutions and dispersions, and methods of the present invention providea coating on the metal surface which is effective in enhancing thecorrosion resistance and paint adhesion characteristics of the metalsurface whether previously conversion coated or not. A further and moredetailed understanding of this invention can be obtained from thefollowing disclosure. All parts and percentages are by weight unlessotherwise indicated.

The need for applying protective coatings to metal surfaces for improvedcorrosion resistance and paint adhesion characteristics is well known inthe metal finishing art as well as in other metal arts. Traditionally,metal surfaces are treated with chemicals which form a metal phosphateand/or metal oxide conversion coating on the metal surface to improvethe corrosion resistance and paint adhesion thereof. The conversioncoated metal surfaces are also generally rinsed or post-treated with asolution containing a hexavalent chromium compound for even greatercorrosion resistance and paint adhesion.

Because of the toxic nature of hexavalent chromium, expensive wastewatertreatment equipment must be employed to remove the residual chromatesfrom plant effluent to comply with environmental regulations and toimprove the quality of rivers, streams, and drinking water sources.Hence, although the corrosion resistance and paint adhesioncharacteristics of conversion coated metal surfaces can be enhanced byan after-treatment solution containing hexavalent chromium, thesedisavantages in recent years have lead to much research and developmentin an effort to uncover effective alternatives to the use ofpost-treatment solutions containing hexavalent chromium. One alternativeto the use of hexavalent chromium involves the use of derivatives ofpolyphenol compounds such as poly-vinyl phenol. Suitable derivatives andsuitable treatment solutions are disclosed in the earlier U.S. Pat. Nos.4,517,028, May 14, 1985 to Lindert; 4,376,000, Mar. 8, 1983 to Lindert;and 4,433,015, Feb. 21, 1984 to Lindert; 4,457,790, July 3, 1984 toLindert, et al.; all of which are expressly incorporated herein byreference. Also see the two commonly assigned applications filed thesame date herewith entitled "Treatment And After-Treatment Of Metal WithPolyphenol Compounds", U.S. Ser. No. 128,672; and "Treatment AndAfter-Treatment Of Metal With Carbohydrate-Modified PolyphenolCompounds", U.S. Ser. No. 128,673; both of which are expresslyincorporated herein by reference.

DETAILED DESCRIPTION OF THE INVENTION

In a typical protective metal surface treatment operation employing thisinvention, the metal to be treated is initially cleaned by a chemical orphysical process and then water rinsed to remove grease and dirt fromthe surface. The metal surface is then brought into contact with thetreatment solution of this invention. Alternatively, and preferably,instead of contacting the metal surface with the treatment solution ofthis invention immediately following the cleaning process, a conversioncoating solution is applied to or otherwise used to pre-treat the metalsurface in a conventional manner to form a conversion coating thereon.Then the conversion coated surface is water rinsed and the metal surfaceis brought into contact with the treatment solutions of the presentinvention.

Although solutions and/or dispersions of the invention can beeffectively applied to treated or untreated metal surfaces, speakinggenerally the present invention is particularly useful if the metalsurface has previously been conversion coated and the invention isaccordingly used as a post-treatment; accordingly, as used herein, theterm "post-treatment" means the treatment of a metal surface which isnot bare metal, and preferably has been previously treated with aconventional conversion coating process. Such conversion coatings arewell known and have been described, for example, in Metal Handbook,Volume II, 8th Edition, pp. 529-547 of the American Society for Metalsand in Metal Finishing Guidebook and Directory, pp. 590-603 (1972), thecontents of both of which are specifically incorporated by referenceherein.

The compositions and processes of the present invention are useful intreating a broad range of metal surfaces, including metals havingsurfaces that have been conversion coated with suitable conversioncoatings such as iron phosphate, manganese phosphate, zinc phosphate,zinc phosphate modified with calcium, nickel, or manganese ions.Examples of suitable metal surfaces include zinc, iron, aluminum andcold-rolled, polished, pickled, and hot-rolled steel and galvanizedsteel surfaces. As used herein, the term "metal surface" includes bothuntreated metal surfaces and conversion coated metal surfaces.

The polyphenol compounds of the present inventions are Polymer Materials1 and 2, their salts, and mixtures thereof. The treatment compositionsof the present invention comprise an effective amount of a soluble ordispersible treatment compound (Polymer Material) in a carrier that issuitable for surface treatment, i.e., one that allows the selectedPolymer Material to be deposited or otherwise placed on the surface of ametal. The soluble or dispersible compound employed in the presentinvention is selected from the group consisting of any one of thefollowing Polymer Materials 1 or 2 (characterized below), solutions ordispersions of these Polymer Materials, their salts, and mixturesthereof. Salts include the acid and alkaline salts thereof.

The methods of the present invention comprise contacting a metal surfacewith treatment compositions described herein.

Polymer Materials 1 and 2 are as follows.

POLYMER MATERIAL 1

Polymer Material 1 comprises a homo- or co-polymer compound or materialhaving at least one unit having the formula: ##STR1##

R₁ through R₃ are independently selected for each repeating unit fromhydrogen, an alkyl group having from 1 to about 5 carbon atoms or anaryl group having from about 6 to about 18 carbon atoms;

Y₁ through Y₄ are independently selected for each repeating unit fromhydrogen, Z, --CR₄ R₅ OR₆, --CH₂ Cl, or an alkyl or aryl group havingfrom 1 to 18 carbon atoms; provided at least a fraction of one of the Y₁through Y₄ units is Z. Z is ##STR2##

R₄ through R₁₂ are independently selected for each repeating unit fromhydrogen, an alkyl, aryl, hydroxy-alkyl amino-alky, mercapto-alkyl orphospho-alkyl moety, or --O.sup.(-1) or --OH; provided at least afraction of Z is or forms an amine oxide or hydroxyl amine. Preferably,R₁ or R₄ through R₁₂ are carbon chain lengths up to a length at whichthe compound is no longer soluble or dispersible in a suitable surfacetreatment carrier, such as water.

W₁ is independently selected for each repeating unit from the groupconsisting of hydrogen; acyl; acetyl; benzoyl;3-allyloxy-2-hydroxy-propyl-; 3-benzyloxy-2-hydroxy-propyl-;3-alkylbenzyloxy-2-hydroxy-propyl-; 3-phenoxy-2-hydroxy-propyl-;3-alkylphenoxy-2-hydroxy-propyl-; 3-butoxy-2-hydroxy-propyl;3-alkyloxy-2-hydroxy-propyl; 2-hydroxyoctyl-; 2-hydroxy-alkyl-;2-hydroxy-2-phenyl ethyl-; 2-hydroxy-2-alkyl phenyl ethyl- isopropenyl-propenyl-; benzyl-; methyl-; ethyl-; propyl-; alkyl; allyl; alkylbenzyl-; haloalkyl-; haloalkenyl; 2-chloro-propenyl-; sodium, potassium;tetra aryl ammonium; tetra alkyl ammonium; tetra alkyl phosphonium;tetra aryl phosphonium; or a condensation product of ethylene oxide,propylene oxide, or a mixture or copolymer thereof.

Particularly preferred are final materials wherein at least a fractionof the W₁ include "Z" and/or the final material is based upon a vinylmoiety, α methyl vinyl phenolic moiety, and mixtures thereof. Forexample, vinyl phenol, isopropenyl phenol and derivatives thereof may beused.

It will be appreciated that the depiction above represents a repeatingunit that characterizes the compound or materials of the presentinvention; no terminating end units are depicted. The end group notdepicted of the polymers of the present invention can be selected by theskilled artisan relying upon art-disclosed techniques. For example, theend groups of the polymer may either be those resulting from thespecific polymerization process employed or those intentionally added toalter the polymer characteristics. For example, the end groups may behydrogen, hydroxyl, initiation fragments, chain transfer agents,disproportionation groups, or other similar methods of terminating agrowing polymer chain.

It is appreciated by those skilled in the art that the alkenylphenolicmoieties of the present invention can be either randomly distributedwithin the co-polymer and terpolymer or can be synthisized to constitutea block orientated polymer, depending upon the methods and conditionsused for polymerization.

Polymer Material 2 --Condensate Polymers

By the term "condensation polymers" is meant the following:

A condensation polymer is a material wherein condensable modified forms(modified to be condensable as noted below) of Polymer Material 1 iscondensed with a second compound selected from the group consisting ofphenols (preferably phenol, alkylphenol, arylphenol, cresol, resorcinolcatechol, pyrogallol) tannins (both hydrolyzable or condensed), novolakresins, lignin compounds, or mixtures thereof and an aldehyde, ketone,or mixture thereof, to produce a condensation resin prepolymer productthat is a prepolymer of Polymer Material 2. The modified startingmaterials are modified by initially failing to include the "Z" moietyprior to initiating condensation; an additional modification to make thestarting materials condensable will also be appreciated as necessary inthat Y₁ through Y₄ cannot be Z, --CR₁₁ R₅ OR₆, or --CR₄ R₅ OR₆. The "Z"moiety (as described above) is then added later to these condensationprepolymers by again reacting the condensation prepolymer resin with (1)an aldehyde, ketone, or mixtures thereof, and (2) a secondary amine toproduce an adduct which can react with acid and/or can be reacted withhydrogen peroxide to generate an amine oxide and can be used in water orin an organic solvent.

While this condensation product is described for convenience as beingprepared by a sequential reaction, it will be appreciated that thesematerials can be prepared by carrying out the necessary steps in anyorder, or simultaneously. However, the sequence described is preferred.

The surface treatment solutions of this invention comprise PolymersMaterial 1, 2, or mixtures thereof, which are preferably dissolved ordispersed in a carrier suitable for depositing or otherwise placing thePolymer Material on the surface of a metal, i.e., as a metal surfacetreatment, metal surface post treatment, a paint, protective film, or asa component of any of the foregoing.

These Polymer Materials of the present invention may be made soluble ordispersible in water or organic solvent-type carriers. They maytherefore be employed as a treatment solution when dissolved in water orin an organic solvent such as, for example, ethanol. Preferably,however, the Polymer Material selected is used in aqueous solution as acarrier.

Accordingly, it is highly desirable to provide or improve the watersolubility or water dispersibility of the selected Polymer Material. Inaddition to the use of the amine oxide fraction, this is preferably donewith an acid used for neutralization and/or complexation of a "Z" moietythereof (if in need thereof). Such acids may be organic or inorganic.Useful and preferred acids for this purpose include carbonic acid,acetic acid, citric acid, oxalic acid, ascorbic acid, phenylphosphonicacid, chloromethylphosphonic acid; mono, di and trichloroacetic acid,trifluoroacetic acid, nitric acid, phosphoric acid, hydrofluoric acid,sulfuric acid, boric acid, hydrochloric acid, hexafluorosilicic acid,hexafluorotitanic acid, hexafluorozirconic acid, and the like; these maybe employed alone or in combination with each other and may beneutralized by conventional acid-base reactions or by complexing.

In a highly preferred embodiment, the addition of water to theneutralized, overneutralized or partially neutralized treatmentcompounds mentioned above results in a water soluble or dispersiblesolution or emulsion of the polymer useful for metal treatment.

Alternately, the final Polymer Material compounds of the presentinvention can be made water soluble or dispersible by neutralization ofthe phenolic group with an organic or inorganic base. Suitable bases forthis purpose include tetra-alkylammonium hydroxides such as tetra-butylammonium hydroxide, tetra arylammonium hydroxide, sodium hydroxide,potassium hydroxide and the like.

In a highly preferred embodiment, the final Polymer Material can beprepared such that a sufficient amount or fraction of the "Z" moiety isan amine oxide and accordingly does not require neutralization.

Within such materials, the ratio of any single monomer to any othermonomer can be about 1:99 to about 99:1, preferably about about 5:1 toabout 1:5, and more preferably 1.5:1 to about 1:1.5.

The molecular weight of the polyphenols used in the preparation ofderivatives claimed in the present invention can be a dimer, but maypreferably be low molecular weight oligomers or resinous polymers havingmolecular weights in the range of about 360 to about 30,000 or greater.The upper limit of molecular weight of materials useful in surfacetreatment compositions is generally determined by the functionallimitation that the derivative therefrom must be soluble or dispersiblein the selected carrier. The resulting derivatives of the formulae setforth hereinabove will typically have a molecular weight of up to about2,000,000 with molecular weights within the range of about 700 to about70,000 being preferred.

Typically, the pH of the aqueous solution will vary from about 0.5 toabout 14. Generally the aqueous solution will have a pH of from about2.0 to about 12 both for the stability of the solution and for bestresults on the treated metal surfaces.

It is contemplated that the compositions and treatment solutions of thepresent invention can be used to treat the surface of a variety ofmaterials, particularly metal and plastic or "plastic-like" surfaces.Preferred metal surfaces include iron-, zinc- and aluminum-based metals.Preferred "plastic-like" material surfaces include resin or polymericmaterials, including thermoplastic and thermosetting materials, as wellas natural rubbers, mixtures of these materials, and the like.

The coating applied may be for protection or decorative in nature, ormay be a preparation of the surface for another treatment; it may alsoserve several functions at once.

The thickness of the final dry or cured coating will depend on itspurposes or functions, and may typically range from about 0.0001 mil toabout 25 mils or greater. The typical and preferred metal surfacetreatment (such as a conversion-type protective/paint base coating) isin the range of about 0.05 mil and below, and more preferably about0.0001 mil to about 0.05 mil. When acting as a paint or decorative andprotective surface treatment, the resulting coating thickness is about0.05 mil and above, preferably about 0.05 to about 25 mils, and morepreferably about 0.05 to about 10 mil.

It is further contemplated that the treatment compounds of the presentinvention will generally be used in surface treatment compositions overa wide range of concentrations. It will be appreciated that the levelsof use or useful ranges will vary with many factors well-known to theskilled artisan. Useful levels of the compositions of the presentinvention dissolved or dispersed in a carrier may be in the range ofabout 0.001% to about 80 percent, depending upon the ultimate use. Forexample, when used as a pre- or post-treatment of a metal surface,useful levels typically include a dilute to moderate concentration offrom about 0.001% to about 20%, by weight, preferably about 0.001% toabout 10 percent, by weight, and still more preferably about 0.001% toabout 5% by weight. Practically speaking, a concentration of 0.0025 to1% is preferred in metal surface treatment (compositions especially foriron-, zinc-, or aluminum-based metal surfaces). However, under somecircumstances (for example when transporting or storing the solution orwhen using it in a "dry-in-place" system), a concentrate of the solutionmay be preferred. Higher levels (for example, as high as 80% by weight)may also be employed when the treatment composition is part of a paintsystem.

Of course, the treatment solutions of the present invention can alsocomprise ingredients typically found in other similar treatmentcompositions (e.g., conversion coating compositions) in addition to thepolymer compound. For example, the treatment solution may optionallycomprise an effective amount of a treatment compound according to thepresent invention, and from about 0.001% to about 3.0% of a metal ion.Metal ions useful for metal treatment in combination with polyphenols ofthis invention include first row transition metals generally, GroupIV-B-metals generally, iron, nickel, cobalt, vanadium, chromium,titanium, zirconium hafnium, scandium, yttrium, lanthanum and theirrespective Lanthanoid and Actinoid metals, as well as molybdenum andtungsten. In addition, tin, silicon, and aluminum compounds, and inparticular their oxides, in combination with the materials of thepresent invention can be used to improve both the effectiveness orperformance of the treatment solution in use. Such materials may alsoreduce the time of application of treatment solution to the metalsurface to as short a time as about 2 to 5 seconds as might be requiredon a coil coating line. Complex fluoride materials may also be employed.For example suitable complex fluoride materials include BF₄.sup.(-1),NH₄ HF₂, hexafluoride and the like.

It must be appreciated that the addition of metal ions may result in theformation of polymer-metal ion chelating compounds.

The Polymer Materials of the present invention may also be employed insurface treatment compositions and surface treatment methods other thanthose described above. For example, the Polymer Material of the presentinvention may be employed as a component of a dry-in-place system, apaint system, or as an additive in a system needing a crosslinkingagent.

For example, the Polymer Materials of the present invention may be usedin a film forming composition that includes a pigment, i.e. may be usedas a paint. They may also be employed as an additional component inconjunction with other polymeric materials in a paint system. ThePolymer Materials of the present invention are particularly useful incathodic electrocoat surface treatment compositions. Such protective,functional and/or decorative surface treatment solutions preferablyemploy typical electrocoat/electrodeposition additives at theirart-established levels. The polymer materials of the present inventionmay be employed as a solubilizing polymer and/or binder in anelectrocoat paint. They may be so employed alone or in conjunction withother binder resins. For example, such paint compositions may optionallyinclude pigments (both organic and inorganic); film forming resins;binders such as epoxies, oils, alkyds, acrylics, vinyls, urethanes,phenolics, etc.; and solvents including hydrocarbons, chlorinatedaliphatics and aromatics, alcohols, ethers, ketones, esters; nitratedmaterials; and particulate zinc.

Accordingly, the compositions and materials of this invention can beused alone or in conjunction with other resins as polymeric coatings onsurfaces. These coatings will crosslink or self-crosslink and can beused in conjunction with other crosslinking agents such asmelamine-formaldehyde or urea-formaldehyde resins as well as phenolicresins, epoxy resins, isocyanates and blocked isocyanates. The Mannichadducts can also be used to crosslink with vinyl functionality as ispresent in resins such as diallylmelamines, butadienes, multifunctionalacrylic oligomers, unsaturated fatty acids in alkyd resins, fatty acidmodified epoxy resins, and the like.

Application of the treatment compositions of the present invention inthe treatment step to a metal or other desired surface can be carriedout by any conventional method. While it is contemplated that the metalsurface will preferably be a conversion coated metal surface, thetreatment step can alternatively be carried out on an otherwiseuntreated metal surface to improve the corrosion resistance and paintadhesion thereof.

For example, the treatment composition can be applied by spray coating,roller coating, or dipping. The temperature of the solution applied canvary over a wide range, but is preferably from 70° F. to 160° F. Afterapplication of the treatment solution to the metal surface, the surfacecan optionally be rinsed, although good results can be obtained withoutrinsing after treatment. Rinsing may be preferred for some end uses, forexample, in electrocoat paint applications.

Optionally, the treated metal surfaces is dried. Drying can be carriedout by, for example, circulating air or oven drying. While roomtemperature drying can be employed, the use of elevated temperatures ispreferred to decrease the amount of drying time required.

After drying (if desired) the treated metal surface is then ready forpainting (with or without the Polymer Materials of the presentinvention) or the like. Suitable standard paint or other coatingapplication techniques such as brush painting, spray painting,electro-static coating, dipping, roller coating, as well aselectrocoating, may be employed. As a result of the treatment step ofthe present invention, the conversion coated surface has improved paintadhesion and corrosion resistance characteristics.

EXAMPLE 1

80 Grams (0.67 moles) of poly-4-vinylphenol resin having an averagemelecular weight of Mw=5000 is slowly dissolved in 160 mls of Propasol P( a propoxylated propanol solvent obtained from (Union Carbide Corp.,Danbury, Connecticut) in a one (1) liter resin flask, using a high speedmixer. The resin flask is fitted with a blade stirrer, reflux condenser,and a nitrogen purge. The resin solution is then charged with 51 Gramsof 2-N-methyl-amino-ethanol and 160 mls of deionized water. Gentleheating to 60° C. is started and then 54.3 Grams of a 37% solution offormaldehyde in water is added over a 45 minute period. The reaction isthen heated to 80° C. for 5 hours at which time the formaldehyde leveldrops below 0.1% indicating that the reaction is complete. The reactionmixture is then allowed to cool until a temperature of 40° C. isreached. Then to the above Mannich adduct of poly-4-vinylphenol is added950 Grams of deionized water, and 85 Grams (0.75 moles) of a 30%hydrogen peroxide solution and allowed to react overnight whilemaintaining the temperature at 40° C.

The amine oxide of the Mannich adduct which is formed by this procedureis soluble in water without further neutralization.

What is claimed is:
 1. A composition comprising a surface treatmentcarrier having a homopolymer or copolymer compound dissolved ordispersed therein, wherein said homopolymer or copolymer comprises amaterial having at least about one-sixth of the units having theformula: ##STR3## where Y₄ is: ##STR4##
 2. A composition according toclaim 1 wherein the carrier comprises water.
 3. A composition accordingto claim 1 wherein the carrier is aqueous and the polymer has beenneutralized with an acid.
 4. A composition according to claim 3 whereinthe acid is carbonic acid.
 5. A composition according to claim 3 havinga pH of from about 0.5 to about
 14. 6. A composition according to claim5 having a pH of from about 2.0 to about
 12. 7. A composition accordingto claim 1 wherein said homo- or co-polymer compound comprises about0.001 to about 80% by weight of the final composition.
 8. A compositionaccording to claim 7 wherein said homo- or co-polymer compound comprisesfrom about 0.001% to about 10% of said composition.
 9. A compositionaccording to claim 8 wherein said homo- or co-polymer compound comprisesfrom about 0.001 to about 5% of said composition.
 10. A compositionaccording to claim 9 wherein said homo- or co-polymer compound comprisesfrom about 0.025% to about 1% of said composition.
 11. A compositionaccording to claim 7 wherein said homo- or co-polymer compound comprisesfrom about 1% to about 80% of said composition.
 12. A compositionaccording to claim 5 which additionally comprises a complex fluoridematerial.
 13. A composition according to claim 1 which additionallycomprises a dissolved or dispersed compound that includes compounds oftitanium, zirconium, hafnium, silicon, or mixtures thereof.
 14. Acomposition according to claim 1 which additionally comprises an oxideof silicon, titanium, tin, aluminum, cobalt, nickel, or mixturesthereof.
 15. A composition according to claim 1 which additionallycomprises a paint system additive selected from the group consisting ofa film forming resin, a pigment, a binder, particulate zinc, or mixturesthereof.